Bag with membrane

ABSTRACT

Bag for receiving bulk material and in particular cement, having a bottom seam and an opposite filling end wherein a receiving space is provided between the bottom seam and the filling end provided to receive the bulk material and formed by the bag wall. A de-aeration device is disposed in the bag wall between the bottom seam and the filling end for de-aerating the bag interior after filling. The de-aeration device comprises a semi-permeable membrane inserted in the bag wall. The membrane is air-permeable and water-impermeable.

The invention relates to a bag of a plastic film for receiving bulk materials, having a bottom seam and a head seam.

Construction material bags, in particular for cement or bags fillable with bulk materials are usually made from paper material. To also protect the bagged materials against moisture seeping in, some of these construction material bags are manufactured from a plastic film, e.g. PE film. Thus the bagged goods such as cement can be effectively protected against moisture seeping in during transport and storage. A suitable selection of PE film thickness also takes into account the mechanical stresses during transport and storage so as to prevent the filled and closed bag from tearing.

When filling bulk materials into bags, some air will as a rule also enter the bag. Air tends to be naturally present in bulk materials and it may even be added to the bulk materials to be bagged to obtain better free-flowing properties. However, any air remaining in the bag results in poor stackability of the bags since they do not assume an optimal rectangular shape.

Therefore solutions already exist according to which bags may be configured such that any air entering during filling may escape even after the bags are closed, in particular while in storage, without compromising protection of the filled goods such as cement against moisture and water and at least against spray water.

EP 1 600 399 A1 discloses a bag of a plastic film fillable with bulk materials wherein relating to the lying bag filled e.g. with cement an overlapping area is provided of an inner and an outer plastic film layer wherein the inner plastic layer comprises in one area de-aeration apertures covered by the outer plastic film layer wherein furthermore a second de-aeration aperture is provided in the outer plastic layer and a channel-type connection exists between the first and the second de-aeration aperture. Moreover the first and the second de-aeration apertures are configured staggered in height relative to one another. This plastic film bag thus configured provides a very advantageous option for de-aeration. However, the structure of a bag created thus is relatively complicated and film consumption also increases.

When a bag forming device is installed upstream of the filling process in the packaging machine then bags of variable lengths may be manufactured from a tubular film so as to allow adaptation to current changes. In these kinds of bags an antitack agent is put onto the tubular film in those places where air outlets are intended such that when welding the head or bottom seams no weld seam is made in these spots and thus small air outlets remain. Since antitack agent is expensive, the antitack agent is not applied across the entire length of the tubular film sheet but only at the distances of the bag lengths in those places where the head or bottom seams are made. The drawback of these known bags is, however, that only defined bag lengths are possible. If flexible bag lengths are desired then the antitack agent needs to be applied over the entire length which is costly.

DE 10 2007 018 579 A1 discloses another bag which may be considered flexible and which is intended to be configured suitable for receiving and transporting and storing cement. To provide leakproofness against permeating water while air should be allowed to escape, this bag consists of two entire layers of material one layer of which is formed by a fleece and the other layer is a film. The two material layers are interconnected as in a laminate. Due to the complex structure of layers, manufacturing these bags is complicated and thus expensive. These bags require prefabrication such that their length cannot be flexibly adapted to the filling process during operation.

It is therefore the object of the invention to provide a low-cost bag which is largely water-impermeable but air-permeable.

This object is solved by a bag having the features of claim 1. Preferred embodiments are the subjects of the subclaims.

For the packaging machine a type of a packaging machine is to be employed in which feeding of the bulk material or of cement occurs in particular from above into so-called open bags or open-mouth bags. A configuration of the bag as a valve bag is conceivable as well.

A bag according to the invention consists of at least one bag wall and comprises at least a bottom seam and a filling end. The bag is provided and/or suitable to receive bulk materials and in particular cement. Between the bottom seam and the filling end that is in particular provided on top, a receiving space formed by the bag wall is provided for the bulk material. Between the bottom seam and the filling end at least one de-aeration device is disposed in the bag wall for de-aerating the bag interior after filling. The de-aeration device comprises at least one semi-permeable membrane inserted in the bag wall. The membrane is water-impermeable but air-permeable.

The bag wall preferably consists of at least one plastic film at least in part and it is water-impermeable. The bag wall may comprise at least one tubular film of a plastic material.

The bag according to the invention has many advantages. A considerable advantage is offered by the de-aeration device with the membrane. The bag can be reliably de-aerated while it is concurrently watertight although manufacturing is still low-cost. Not the whole bag is required to be configured air-permeable but it is sufficient for a small surface only to serve for de-aeration.

It is in particular possible to form the bag in a packaging machine immediately prior to filling. In this way the bag length can in particular be adjusted very flexibly since the bag length can at any time be increased or decreased. It is particularly advantageous that the bag can be manufactured from a standard tubular film which is extruded circular in appropriate dimensions. It is not required to manufacture a one-layer film whose edges are placed on top of one another and welded to one another to form a de-aeration channel.

The inventive bag of a plastic film may be provided with a bottom seam and a head seam and be filled with bulk materials such as in particular cement. When filled there is then provided between the bottom seam and the head seam a space of a plastic film surrounding the bulk material and preferably substantially rectangular. To allow contained air to escape, a membrane is inserted into the bag wall or plastic film beneath the head seam.

The de-aeration device comprises at least one de-aeration component with at least one membrane which membrane is watertight but air-permeable.

The de-aeration component is preferably attached to the inner bag wall. Then, increased internal pressure cannot cause the de-aeration component to break off but rather ensures a still tighter seat of the de-aeration component. The forming of a channel between the bag wall and the de-aeration device or membrane attached thereon can also be reliably prevented. The bag is in particular configured such that its configuration from a tubular plastic film is immediately recognizable. In respect of the filling position an approximately rectangular, first cross-section is preferably configured in the bottom area. Beneath the filling end or the head seam a second, again approximately rectangular, cross-section is formed near the filling range in respect of the packaging machine. When the bag is filled the first and the second cross-sections correspond to one another at least substantially.

In particularly preferred configurations the bag wall is provided with gussets. Particularly preferably corner weld seams are provided at least at one end and in particular at both ends of the bag wall to ensure a rectangular shape of the filled bag. In this way good stackability of the bags is achieved to thus allow secure and stable stacking of a plurality of bags on pallets while concurrently retaining an esthetically attractive pallet shape.

Preferably the de-aeration device is disposed in the top wall. This allows high de-aeration performance and prevents clogging during filling since as a rule the top wall remains above the filling level during filling.

As another configuration variant valve bags offer themselves comprising at the filling end a filling valve by means of which the valve bag is placed on a filling spout of a packaging machine. The bag is filled through the filling valve. All of the configurations provide that a piece with a membrane that is relatively small relative to the entire surface of the bag wall and in particular of the bag is preferably inserted in the area beneath the filling end or beneath the head seam. The membrane is particularly preferably configured to be semi-permeable or at least comprises a semi-permeable area or section.

The area proportion of the membrane relative to the entire bag wall surface and in particular to the bag is in particular less than 10% and preferably less than 1%. The area proportion may even be smaller still and may in particular lie between 0.05% and 0.5%.

In particular the de-aeration performance of the membrane, given an excess pressure in the bag interior of e.g. approximately 50 mbar, is higher than 0.01 liters/minute on the whole, preferably the de-aeration performance is higher than 0.25 liters/minute and it may for example lie between 0.5 liters/minute and 20 liters/minute. Still higher de-aeration performances are conceivable as well. In the region of the membrane the plastic film is broken open entirely where possible.

The membrane is in particular configured semipermeable. Employing PTFE or expanded PTFE (ePTFE) is possible.

The solution according to the invention provides a bag which can be formed in particular from a tube of a plastic film which has been wound onto a roll. The film roll may be received at the packaging machine.

After unwinding the tubular goods from the roll a welded or glued seam is preferably formed as a bottom seam. A sewn seam which is in particular sealed is conceivable as well. After separating from the unwound tube stock the bag is fed to the filling station of the packaging machine as a pre-fabricated bag. Such feeding to the filling station of the packaging machine may only be interrupted in that an interpositioned station provides for a relatively small area of a membrane to be inserted in the region beneath the head seam to be made after filling wherein a connecting seam may be assumed in the shape of e.g. a welded seam or a glued seam.

The membrane may be inserted close to the head seam. In the case of gusseted bags the membrane may be inserted in a gusset. The membrane or at least one membrane may also be inserted in the region of the corner weld of the gusset.

In the region where the membrane is inserted the plastic film of the bag is preferably cut initially or else cut out. The cut-out area may be somewhat smaller than the dimensions of the piece with the membrane so as to take into account the requirements of forming a robust seam e.g. by gluing or welding or the like. When the filling operation is terminated, the head seam is formed.

Other configurations may provide for a pre-fabricated bag manufactured from a tubular film or flat sheeting.

The filling operation is preferably controlled such that the quantity of any air trapped in the filled bag is not very large. It may suffice to insert in the region beneath the head seam an approximately rectangular piece of a membrane e.g. being between 0.3 cm and 15 cm in length and between 0.3 cm and 15 cm in width. The membrane surface is preferably between 0.5 square centimeters and 5 or 10 square centimeters.

Other geometric membrane shapes such as oval, circular, polygonal may be assumed. What is decisive is only to provide a certain size of the membrane attached relative to the entire bag surface, in particular for the air exit out of the filled material bag. Or else it is conceivable for two or more membranes to be inserted.

The de-aeration component may comprise a holder frame surrounding the membrane.

A membrane considered suitable is air-permeable and is preferably absolutely watertight to external water. Optionally the membrane may be permeable to water vapor. These membranes of polytetrafluoroethylene (PTFE) may be used in a kind of laminate with a fabric or textile layer and are available in the market. The invention is, however, not intended to be limited in respect of these products usual in the market.

Other advantages of the present invention become clear in the exemplary embodiment which will be discussed below with reference to the accompanying figures.

FIG. 1 a perspective view of a bag according to the invention;

FIG. 2 an enlarged sectional view of the head end of the bag from FIG. 1;

FIG. 3 another bag according to the invention in a top view;

FIG. 4 a side view of the bag according to FIG. 3; and

FIG. 5 a schematic view of a bag configured as a valve bag.

The inventive bag 1 is manufactured from a tubular material and in particular from a film tube 21 of a plastic film 1 a. In preferred configurations the tubular material 1 a consists at least in part or in at least one layer of a polyethylene film which may comprise additional coating. The bag 1 may consist of other materials as well. It is conceivable to use paper bags the bag walls of which show little de-aeration performance only. It is also conceivable to use bags of woven ribbons.

The properties and features of the inventive bag 1 are also based on its manufacturing steps. Therefore the exterior surface 1 b of the bag substantially corresponds to the exterior surface of the bag wall 15 or to the tubular plastic film 1 a from which the bag 1 is formed.

A packaging machine (not shown) comprises a bag forming station. The tube wound in layers onto a roll or reel is pulled off and provided with a bottom seam 2 transverse to the pulling-off direction which shows a distance from the take-off edge of the intended fill height of the bag 1 which is adapted and presently variably adjustable during the filling process. A variably adjustable bag length allows to flexibly adapt the film consumption in production to the current requirements. In particular can the bag length be decreased if a projecting edge forms at the head end 10. This leads to considerable savings regarding costs for the bags.

Forming this transverse or bottom seam 2 at the bottom end 22 is in particular done by welding or else it may be done by gluing or another joining process.

Prior to or following the making of the bottom seam 2 separation from the remaining tubular material of the plastic film 1 a to be fed from the roll is done in the immediate vicinity of the bottom seam 2 to be made or having been made.

Now the bag 1 open at the top filling end 7 or the open-mouth bag is—in a suitable way prior to filling—provided with a semipermeable membrane 4 a of a suitable size and suitable contour. Preferably one selects a rectangular or round or rounded strip 4 or a circular blank 4 of suitable dimensions e.g. 0.5 cm to 10 cm in length and 0.5 cm to 5 cm in width. Other shapes of contour of the approximately same area may be selected. In a specific embodiment a round membrane 4 a of 2.0 cm in diameter is used and glued onto the inner bag wall 6.

In specific configurations the strip 4 is aligned approximately in the center on the side relative to the filling end 7 or to the beginning and the end of the intended head seam 3. With other contour shapes an analogous process is employed.

Dr else, the strip 4 may be provided in the region of a gusset 14.

In the region of the membrane 4 a at least one aperture 11 is preferably provided in the bag wall 1 a through which the air escaping from the bag 1 and through the membrane 4 a can exit.

Preferably the strip or the circular blank 4 is configured as an adhesive label 5 which is glued onto the inner wall 25 or the inside 6 of the bag wall 1 a from the inside. Attaching on the inside 6 additionally enhances the sealing effect and also causes a decrease of the stresses on the glued or welded seam 12. The strip 4 may also be attached to the outside 9 of the bag 1.

While the membrane 4 a is preferably disposed in the front wall or top wall 19, it is also possible to provide the membrane 4 a in the side wall 24. The de-aeration device 16 or the membrane 4 a is particularly preferably disposed in the narrow side wall 26 as it is schematically illustrated in dashed lines in FIG. 1. The membrane 4 a is then preferably disposed in the vicinity of one end in the region of the gussets 14. Preferably the membrane 4 a is disposed in the vicinity of the filling end where the membrane 4 a is protected by the overhanging top wall 19 at the head end 10. The adhesive label 5 or the strip 4 is preferably attached to the head end 10 in the region of the intended top wall 19. In this way the membrane 4 a remains largely unstressed by the bulk material to be filled in during the filling process so as to ensure reliable, fast de-aeration.

The strip 4 or a similar component in another contour shape with the membrane 4 a is connected at the respective position of the bag-type, unfinished bag 1 by means of a seam 5. One may chose e.g. a welded seam or a watertight, glued seam. The membranes 4 a are particularly preferably glued on as it is done e.g. with adhesive labels. Within the seam contour to be formed a corresponding area size of plastic film must be exposed. Such exposing by cutting or separating may be done in conjunction with forming the seam. Even after inserting the strip 4 with the membrane 4 a in an appropriate position an unfinished bag is still present which is, however, prepared for the filling process with bulk material such as cement.

After putting in the bulk material such as cement the head seam 3 is made e.g. by welding.

FIG. 1 shows at 2 the bottom seam 2 made or attached which is located in the immediate vicinity of the separating line (not bearing a reference numeral) opposite the delivered tubular goods.

The bag 1 made of the tubular plastic film 1 a assumes a quasi rectangular, non-interrupted shape. With filling, a flat cross-section is assumed within the circumference of the originally tubular plastic film 1 a without requiring the bottom seam 2 to be prepared by folding the tubular material in its end region. The use of tubular material with gussets 14 and making corner weld seams 13 ensures a rectangular-shaped form 23 of the bag 1 after filling. Such a bag 1 is readily stackable and thus easily transportable and storable.

The head seam 3 which is also evident in FIG. 1 closes the filled bag 1.

FIG. 3 shows a bag 1 with gussets in the tubular material such that the seam end regions of the bottom seam 2 comprise four layers compared to two layers of the (substantially comprising a greater length) center region of the seam. Then the seam end regions of the head seam 3 also comprise four layers compared to two layers of the (substantially comprising a greater length) center region of the seam.

In FIG. 2 an enlarged sectional side view of the head end 10 of the bag 1 is illustrated. It can be clearly seen that the strip 4 with the membrane 4 a presently configured as an adhesive label 5 is attached to the inside 6 of the bag 1 from the inside. The glued seam 12 surrounds the membrane 4 a and the central opening 11 in the bag wall 1 a.

The receiving space 8 which after filling is filled with a bulk material can be reliably de-aerated through the membrane 4 a.

It is also possible to purchase the bag 1 pre-fabricated and to feed it to the packaging machine as a finished, open bag. The pre-fabricated bag may be provided wound up.

FIG. 3 shows another configuration in which the membrane 4 a is disposed on the outside 9 of the bag 1 in the shape of a strip 4 or an adhesive label 5. Again the membrane 4 a is provided in the region of the head end 10.

Beneath the head seam 3 at least one strip 4 with the membrane 4 a is attached. The seam 5 already described above in respect of the manufacturing process serves therefor. The membrane 4 a is preferably disposed in a region in which the rectangular cross-section has already formed.

On the whole a bag 1 is provided which in particular consists of a plastic film 1 a. The bag 1 is formed by a tubular material. The tubular material may be configured as a film tube 21 and be unwound from a roll at an FFS machine to form the bag 1 from the film material. The film tube 21 may be provided with gussets 14.

The bag 1 comprises at its bottom end a bottom wall 18 with the bottom seam 2. The bag interior 20 is surrounded by the bag wall 15. At the filling end 7 a head seam 3 is at the head end 10 in the top wall 19 in a filled and closed state. The de-aeration device 16 with the membrane 4 a is inserted in the top wall 19.

The surface 1 b of the bag 1 is provided with at least one de-aeration device 16 which is attached to the bag wall in particular from the inside. The de-aeration device serves for de-aerating the interior of the bag after filling. The de-aeration device 16 comprises at least one semipermeable membrane. The membrane 4 a is air-permeable and water-impermeable.

In the vicinity of the filling end a head seam is provided. The cross-section of the filled bag 1 is in particular nearly rectangular near the bottom seam and near the head seam.

The de-aeration device may comprise a de-aeration component 17 or else multiple de-aeration components 17 each having at least one membrane 4 a. Each membrane 4 a may consist of polytetrafluoroethylene at least in part.

Preferably the bag wall 15 is provided with gussets 14 and at its ends 10 and 22, with corner welds 13 to ensure a rectangular shape 23 of the filled bag 1.

The de-aeration device 16 is particularly preferably disposed in the top wall 19 near the filling end 7.

FIG. 5 shows a simplistic view of a bag 1 configured as a valve bag which is provided with a feed valve or filling valve 27. The bag 1 according to FIG. 5 is placed onto a filling spout of a packaging machine with the filling valve 27 and through the filling valve 27 it is filled with the bulk material to be bagged.

With the bag 1 illustrated in FIG. 5 the de-aeration device 16 with the membrane 4 a is preferably disposed beneath the filling valve 27 since in this place there is relatively low stress during filling and also relatively low exposure to dust during the filling process. The bag 1 configured as a valve bag may be pre-fabricated separately. In manufacturing the membrane 4 a with the de-aeration device may be inserted in the bag wall.

LIST OF REFERENCE NUMERALS

-   1 bag -   1 a plastic film -   1 b bag surface -   2 bottom seam -   3 head seam -   4 strip, circular blank -   4 a membrane -   5 adhesive label -   6 inside -   7 filling end -   8 receiving space -   9 exterior -   10 head end -   11 opening -   12 glued seam -   13 corner weld seam -   14 gusset -   15 bag wall -   16 de-aeration device -   17 de-aeration component -   18 bottom wall -   19 top wall, front wall -   20 bag interior -   21 film tube -   22 bottom end -   23 rectangular shape -   24 side wall -   25 inner wall -   26 narrow side wall -   27 filling valve 

1. Bag for receiving bulk material and in particular cement, having a bottom seam and a filling end opposite, wherein a receiving space is provided between the bottom seam and the filling end for receiving the bulk material and formed by the bag wall wherein at least one de-aeration device is disposed between the bottom seam and the filling end in the bag wall to de-aerate the bag interior after filling, characterized in that the de-aeration device comprises at least one semipermeable membrane inserted in the bag wall and which is air-permeable but water-impermeable.
 2. The bag according to claim 1 wherein the bag is provided with a head seam near the filling end.
 3. The bag according to claim 2, wherein the cross-section of the filled bag is nearly rectangular near the bottom seam and near the head seam.
 4. The bag according to claim 1 wherein the bottom seam and/or a head seam comprise at least one weld seam and/or glued seam.
 5. The bag according to claim 1 wherein the de-aeration device comprises at least one de-aeration component with the at least one membrane.
 6. The bag according to claim 5 wherein the de-aeration component is disposed at the inner bag wall.
 7. The bag according to claim 5 wherein the membrane consists of polytetrafluoroethylene at least in part.
 8. The bag according to claim 1 wherein the bag wall consists of a plastic material at least in part.
 9. The bag according to claim 1 wherein the bag wall is provided with gussets.
 10. The bag according to claim 1 wherein the bag wall is provided with corner welds at the ends to allow a rectangular shape.
 11. The bag according to claim 1 wherein the de-aeration device is disposed in the top wall.
 12. The bag according to claim 1 wherein the de-aeration device is disposed in one of the narrow side walls.
 13. The bag according to claim 1 wherein a de-aeration component is inserted into the bag wall by means of a seam wherein at least one opening is provided in the bag wall within the seam contour and wherein the seam is preferably configured as a welded seam or a glued seam or an adhesive area.
 14. The bag according to claim 1 wherein a surface of a de-aeration component is less than 1% and in particular less than 0.5% of the bag wall surface, and/or wherein the de-aeration performance is higher than 0.01 liters/minute and in particular higher than 0.25 liters/minute.
 15. The bag according to claim 1 wherein a de-aeration component comprises a holder frame surrounding the membrane. 